1. Field of the Invention
The present invention relates to aluminum-based alloys suitable for high temperature applications including aerospace. The alloys can be processed to various product forms, e.g., sheet, thin plate or extruded, forged or age-formed products.
2. Description of Related Art
Aluminum alloys are widely used in engineering structures and components where low weight or corrosion resistance is required. Wrought alloys are commonly used in the manufacture of aircraft structural components, such as underwing applications. Cast aluminum alloys yield cost-effective products, although they generally have lower tensile strengths than wrought alloys. Aluminum alloys are particularly important in aerospace manufacturing for their high strength-to-weight ratio, as well as in the manufacture of lightweight, high-end automobile components (e.g., engine block or wheel/brake components). However, due to the low melting point of aluminum, many aluminum-based alloys have the drawback of limited mechanical properties at high temperatures. For example, underwing metallic structures and components in modern commercial aircraft are intermittently exposed to elevated temperatures during flight, which over time results in significant degradation of the alloy strength and toughness. In addition, there is a continuing push for better efficiency and fuel economy; however, higher efficiency engines run much hotter such that traditional aluminum-based alloys can no longer be used due to significant decreases in strength, ductility, and toughness over time. One alternative has been the use of much thicker and heavier aluminum pieces to counteract the loss of strength over time. However, this added weight defeats the purpose of the higher efficiency engine and also adds to the initial cost of the piece. Titanium alloys have been proposed as alternatives to aluminum-based alloys, due to their high tensile strength and toughness (i.e., damage tolerance, even at extreme temperatures), lightweight, extraordinary corrosion resistance, and ability to withstand extreme temperatures. However, due to the increased expense of using titanium over aluminum, the development of aluminum-based alloys with improved elevated temperature properties remains important.
Attempts to develop aluminum alloys having one or more improved properties (e.g., higher strength-to-weight ratio) for casting or wrought processing, often results in sacrificing other properties of the alloys (e.g., fatigue performance or damage tolerance). Numerous alloys have been proposed. One of the most common cast aluminum alloy systems, is Al—Si (e.g., AlSi7Mg), where high levels of silicon (>4%) contribute to good casting characteristics. Another aluminum alloy system with good mechanical properties is Al—Li. However, Al—Li alloys are not only more expensive, but carry a high risk of fire and explosion, complicating their manufacture. Thus, there remains a need in the art for aluminum alloys with improved properties that do not suffer from the drawbacks of previously proposed systems.